Monday, March 12, 2012

Every year, the International Sea Turtle Society convenes
for the annual conference where science research, conservation, and all the
inspiring and creative work combining these areas is shared among sea turtle
biologists and enthusiasts from around the world. Last year, the 31st Annual International Sea Turtle
Symposium (ISTS) was hosted in our home town of San Diego! This year, the ISTS
is in our neighbor to the south, Mexico, in the beautiful town of Bahias de Huatulco
in the state of Oaxaca.

At last year’s ISTS, I shared my research that was focused
on the green sea turtles (Chelonia mydas)
that live in the San Diego Bay as well as a project designed to
help sea turtle conservation groups be as efficient as possible (A Diagnostic Tool for Marine Turtle Conservation Success). This year at the conference,
which officially kicks off tomorrow, Sunday, I’ll be sharing my research that I’ve
begun for my doctoral research.

Over the next week, I’ll be sharing not only more of the
research I’ll be doing, but I’ll also be sharing all of the incredible talks
and events which I’ll be participating in as part of the 32nd Annual ISTS.

On Sunday and Monday I’ll be participating in a two-day workshop all
about climate change and sea turtles that is being run by biologist Marianne
Fish of the WWF. Then on Monday evening, the full ISTS begins. Tuesday-Friday
will be filled with talks, discussions and workshops. On Wednesday I’ll be
helping put on a workshop for local students that is being run by Frances
Kinney of the Ocean Connectors program, and on Thursday we are hosting a
similar workshop for local teachers. Saturday and Sunday will be opportunities
to explore the region and its incredible wildlife.

Sunday, March 4, 2012

This year, the 32nd annual International Sea Turtle Symposium (ISTS) is being held in Huatulco, Oaxaca Mexico the week of March 11-17. At this year's annual meeting, I will be presenting my work that I've begun for my doctoral dissertation.

The East Pacific green turtle (Chelonia
mydas) a.k.a. 'black turtle' population along the Pacific coast of Mexico
is listed separately from global green turtles on the U.S. Endangered Species
Act, and this population is currently considered Endangered. Cross-border
international efforts to protect this population over the past 30 years have curbed
the dramatic population decline that was representative of the black turtles in
the last century. Green turtles of Pacific Mexico, like green turtles around
the world, are subject to
varying threats, presenting managers with unique conservation challenges. Distinct
risks, environmental conditions and population trends necessitate specific management
strategies for these separate populations. Assessing basic turtle biology
during the entire life cycle has been identified as a key research priority for
all populations of marine turtles. The age-at-settlement, when juvenile turtles
undergo an ontogenetic shift from oceanic to neritic habitats, remains unknown
for most marine turtle stocks, and better information on the timing of this
shift will facilitate more accurate risk assessment and population estimates
for management purposes.

A humerus bone of a dead-stranded green sea turtle (Chelonia mydas)

Stable isotope analysis has been
applied to marine turtle humerus bones and scute keratin to identify foraging
habitat of marine turtle populations across the globe. This is made possible due to the fact that tissues such as bone and
keratin are comprised of nutrients garnered in foraging areas, and these hard inert
tissues record isotope signatures from multiple years’ worth of foraging. When an animal moves among spatially discrete food
webs that are isotopically distinct, stable isotope values of its tissues can
provide unambiguous information about its previous location. Additionally, skeletochronology
has been used to estimate age of marine turtles. Using the two together, on
adjacent bone or scute samples, allows a determination of the stable isotope
values of specific growth layers, which in the case of humerus bones are
believed to be annular. Thus, isotopes and skeletochronology has the potential
to decipher what habitat types are occupied during sequential years of life. Stable
carbon (δ13C) and nitrogen (δ15N) isotope analysis will be conducted on humeri
bones from green turtles stranded along the Pacific coast of the Baja
California Peninsula, Mexico and from within the Gulf of California. These data
will later be linked with skeletochronology and isotope analysis of bone and
scute material to elucidate ontogenetic shifts of individual turtles from green
turtles in this region. The goal of our research is to gain a better
understanding of the duration of the pelagic juvenile stage (i.e. the “lost
years”) of green turtles along the Pacific coast of Mexico. Through this unique
combination of stable isotope analysis of bone and scute with skeletochronology
we hope to determine the age-at-settlement for this recovering population of
green turtles and improve understanding of green turtle ontogeny.

About Me

Cali is a Postdoctoral Fellow at University of California, San Diego's Ecology program, having received her Ph.D. in Ecology, Behavior
& Evolution. She is a graduate of UCSD's Scripps Institution of Oceanography, where she received her Masters in Marine Biodiversity and Conservation. Her work conducting environmental monitoring in San Diego includes assisting NOAA researchers monitor the population of green sea turtles in the San Diego Bay. The work highlighted on this blog is in partnership with NOAA's Southwest Fisheries Science Center (see links for more information).